DESCRIPTION (from the application): We have identified a specialized form of RNA polymerase II that controls expression of subsets of genes in response to extracellular signals. Normal patterns of growth and development in single and multicellular organisms require reception of extracellular signals and transmission of this information to the nuclear transcription apparatus. This generates unique patterns of gene expression defining developmental stages and differentiated tissues. Errors in these pathways result in disease including developmental defects and cancer. We have shown that the yeast protein kinase C/MAP kinase signaling cascade communicates with its target genes through this novel form of RNA polymerase II, which includes the products of the PAF1, CDC73, HPR1 and CCR4 genes. Mutations of factors in this complex lead to misregulated expression of genes important for cell integrity, and genes involved in DNA synthesis and repair. A hypothesis to be tested in this proposal is that the Paf1 complex also plays a role in the developmental pathway of meiosis and sporulation. The complete composition of the Paf1 complex will be determine using mass spectrometry, and the full spectrum of genes regulated by the complex will be analyzed with DNA microarrays. Promoter elements requiring the components of the Paf1 complex will be identified and tested in vitro. DNA binding regulatory factors that are modified by signals from the MAP kinase pathway will be determined and their interactions with the Paf1 complex will be characterized. The role of the Paf1 complex during the cell cycle, and in meiosis and sporulation will be tested by analyzing gene expression patterns and characterizing the composition of the complex during these transitions. Homologues of Paf1 complex encoding genes have been recently identified in worms, flies and humans. Therefore, understanding how this specialized form of RNA polymerase II functions to differentially regulate subsets of genes in yeast will help to direct studies of complex signaling pathways in eukaryotes in general.